In multimedial mobile terminal equipment, such as. e.g., digital cameras, mobile telephones, etc., the available storage space is very limited. Multimedial data, such as e.g., image and video data, require a lot of storage space, which is available in mobile terminal equipment only to a very limited degree. Once the maximally available storage space has been filled, the user of the equipment must decide whether he wants to delete the old data content or refrain from storing new data. This fact shall be explained based on the example of a digital camera. Before taking a photograph, the user must adjust on the camera which image resolution the photograph is supposed to have. Modem digital cameras offer multiple picture resolutions to chose from, e.g., 640×480, 800×600 or 1024×768 image points (pixels). If the user selects a lower resolution, e.g., 640×480 pixels, more photographs can be saved to the storage medium of the camera. However, these photographs are then of a lower quality. If the user opts for a higher resolution e.g., 1024×768, only a few photographs will fit on the storage medium. If the user wants to continue taking photographs when the storage medium is full, he must first delete photographs and free storage space by converting existing photographs with a high resolution into photographs with a low resolution and saving them as such. In both cases the available storage space is not optimally used.
The explained example and its associated shortcomings are also applicable to other mobile terminal equipment, e.g., to audio and video terminals.
In EP 0 999 706 A2, a method is known for the dynamic management of a storage device for digital image data that is based on a so-called “embedded coding” of the bitstreams. in this method the image data is sorted according to the importance of the image information, in such a way that the bitstreams are coded such that the most important image information is stored first and the least important image information is stored last. When the storage medium is full, additional image information can be stored only in such a way that the least important image information of the image data that has been stored until then is deleted, so that additional storage space is freed.
A similar method is revealed in U.S. Pat. No. 6,246,797 A, wherein a DCT transform or wavelet transform is used in this case for coding of the image data. If storage space is to be freed, the image information of a complete image must be re-coded in each case, which requires a relatively large amount of computing effort.
U.S. Pat. No. 5,867,602 A reveals a method of coding digital data with the aid of a reversible wavelet transform. An application of this method for storage space management of a storage medium is not described.
All methods known from the prior art do not use a coding method that is based on a prioritized pixel transmission.